Have you tried showing all active hotspots in the scene? (Click on the lens icon that appears as you move your cursor to top right of your game screen.)
There should be a hotspot that appears on the side of the crates to indicate the crane controls. Examine the crane controls and your character will comment and lower the hoist. Then you should be able to attach the hose.
Did you already attach the hose to the pulley on the floor, and to the bars at the top of the crates?
If you still have problems, let us know.